Palladium/Copper-Catalyzed Aerobic Intermolecular Cyclization of Enediyne Compounds and Alkynes: Interrupting Cycloaromatization for (4 + 2) Cross-Benzannulation

A tandem
coupling–ketooxygenation reaction of readily accessible
enediyne–carboxylic compounds with inner alkynes has been developed
that utilizes the PdCl2/CuBr2 catalytic system
under an O2 atmosphere and assembles a class of isoindolinones
and o-acylbenzoic acids. The two oxygen atoms are
regioselectively incorporated into enediyne units at the 1- and 6-positions
from atmospheric molecular oxygen and H2O, respectively,
during the present process. This study uncovered a formal [4C + 2C]
benzannulation–diketonization of enediynes and alkynes via
a coupling and decoupling strategy.